Silver halide diffusion transfer process



United States Patent SEVER HALIDE DIFFUSION TRANSFER PROCESS Louis Maria De Haes, Edegem, Belgium, assignor to Gevaert Photo-Producteu N.V., Mortsel-Antwerp, Belgium, a Belgian company No Drawing. Filed Aug. 5, 1963, Ser. No. 300,101 Claims priority, application Netherlands, June 15, 1962,

279,797; Aug. 3, 1962, 281,744 15 Claims. (CI. 96-29) The present application is a continuation-in-pa-rt of our application Ser. No. 288,433 filed June 17, 1963, now abandoned.

The present invention relates to the silver complex diffusion transfer process of producing images and more especially to an accelerated process.

According to the known silver salt diffusion transfer rocesses the principle of which is described in British patent specifications 614,155 and 654,130 and in German patent specification 887,733, a light-sensitive silver halide emulsion layer is exposed to an image and then pressed while in wet condition into contact with a specially prepared receiving material in the presence of developer and a substance or substances which dissolve the silver halide in complexed form. The exposed image areas are developed and do not undergo any further change. The undeveloped silver halide in the unexposed areas is complexed or solubilized by a compound or compounds present in the liquid or in the receiving material, transferred by diffusion into the receiving layer of the said image-receiving material and converted therein to metallic silver. The conversion is promoted by the catalytic action of developing nuclei. In this way, an image is formed in the receiving material and is apparent after separation of the latter from the light-sensitive material. The developing nuclei normally consist of finely divided metal or metal sulphide. They can be incorporated in the image-receiving material during its manufacture or formed in situ therein during the diffusion transfer process.

Many proposals have been made and adopted with a view to improve the processing in the diffusion transfer process.

An interesting improvement is the use of a processing liquid containing no developer components as known from British patent specification 767,978. According to this patent specification an image-receiving material containing sodium thiosulfate and hydroquinone and a lightsensitive material containing a non-migratory developing substance are used, the processing liquid being an aqueous solution of sodium hydroxide and sodium sulfite.

Such a process has various advantages, for instance, a longer shelf life for the processing bath and a more permanent quality of the white color of the obtained copies. However, the process according to the said British patent specification possesses the disadvantages of a delay of the diffusion transfer image formation and of the formation of fog in the light-sensitive material which probably isv due to the nonmigratory developing substances present.

It has now been found that according to the silver complex diffusion transfer process very good images can be obtained rapidly with an image-receiving material containing developing nuclei for the complexed silver halide or substances capable of forming such nuclei in situ and with an aqueous processing liquid containing alkali, by using a superadditive developer combination consisting of hydroquinone as a principal developing substance and a 3-pyrazolidone developing compound as a secondary developing substance, the principal developing substance being incorporated in the image-receiving material and the secondary developing substance being incorporated in the light-sensitive material.

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It has further been found that the said process can be carried out by wetting only the light-sensitive material with treating liquid and then pressing it against a dry image-receiving material when using a light-sensitive material which comprises in addition to the light-sensitive silver halide emulsion layer a water-permeable top layer from which at least a thin stratum is transferred to the image-receiving material when separating said both materials.

The secondary developing substance is a poor developing substance in itself so that it cannot produce fog in the light-sensitive material, whereas the superadditive combination has a so surprisingly rapid effect that the diffusion transfer process according to this invention occurs as rapid as in a process wherein the developing substances are incorporated in the bath. Further, a process according to this invention possesses the advantages already cited above of a diffusion transfer process without developing substances in the processing bath.

3-pyrazolidone compounds which are suited for being used according to this invention mostly correspond to the following general formula:

Rrl wherein:

R represents an aryl radical or a substituted arvl radical,

R represents a hydrogen atom or an acyl radical such as an acetyl radical, and a each of R R R and R (the same or different) repreresents a hydrogen atom, an alkyl radical, a substituted alkyl radical, an aryl radical or a substituted aryl radical.

Good results can be obtained with the following compounds corresponding to the above formula:

l-phenyl-3 -pyrazolidone V l- (m-tolyl) -3 -pyrazolidone 1-phenyl-2-acetyl-3-py-razolidone 1-phenyl-4-methyl-3-pyraz0lidone 1-phenyl-5-methyl-3-pyrazolidone 1 -phenyl-4,4-di-methyl-3-pyrazolidone 1-pheny1-5,5-dimethyl-3-pyrazolidone 1,5 -diphenyl-3-pyrazolidone 1- (m-tolyl) -5-phenyl-3-pyrazolidone 1- p-tolyl -5-phenyl-3-pyrazolidone.

For alkalizing the processing liquid used in a process according to the present invention, basic compounds are added such as sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, sodium carbonate, sodium phosphate, etc.

For a compound which is weak in this respect, e.g. sodium phosphate, it is appropriate to use an amount of the anhydrous salt of from 50 to 200 g. per liter. In the case of a compound which imparts a high degree of alkalinity, eg sodium hydroxide, an amount of from 5 to 20 g. will suffice.

Anyhydrous sodium sulfite may be incorporated into the processing liquid in an amount e.g. of from 10 to 40 g. per liter.

The processing liquid may further contain other usual ingredients such as sodium bromide, calcium sequestering compounds and black-toning agents e.g. l-phenyl-S- mercaptotetrazole or similar products such as those described in the British patent specification 561,875 and the Belgian patent specification 502,525, but need not contain any developer substance.

An image-receiving material according to the invention may e.g. consist of a support which is impregnated with development nuclei or with a substance or substances for forming such nuclei in situ. Preferably, however, an image-receiving material for being used in a process according to this invention comprises a non-light-sensitive colloid layer for instance a water-permeable organic colloid layer such as a gelatin layer, on a paper or other support, the colloid layer incorporating the development nuclei or substances which can form such nuclei in situ during the diffusion transfer process. By developing nuclei for complexed silver halide, nuclei for physical development as well as ingredients for chemical image formation are meant.

Development nuclei for silver halide complexes suitable for promoting the formation of the silver containing image in the image-receiving layer are the sulfides of heavy metals e.g. of antimony, bismuth, cadmium, cobalt, lead, nickel, silver and zinc. Selenides, polysulfides, polyselenides, mercaptans, stannous halides, heavy metals or their salts and fogged silver halides are also suitable for this purpose. The complex salts of lead sulfide and zinc sulfide are effective either in themselves or mixed with thioacetamide, dithiobiuret and dithiooxamide. Among the heavy metals silver, gold, platinum, palladium and mercury are to be mentioned, preferably in their colloidal form. The noble metals among them are the most active.

The image-receiving layer and/ or a layer which is in effective contact with this image-receiving layer (i.e. from which the incorporated compounds in due time can diffuse to the image-receiving layer) incorporate hydroquinone as a principal developing substance. As a preservative for hydroquinone and in order to obtain diffusion transfer copies keeping a white background in aging, the imagereceiving material may comprise at least one compound selected from the group consisting of alkali metabisulfites such as potassium metabisulfite, water-soluble inorganic bisulfites and water-soluble aldehyde bisulfites. Such an image-receiving material is described in the German patent specification 1,129,052. The image-receiving material may also contain usual ingredients such as sodium sulfite, a complexing agent for silver halide such as sodium thiosulfate and black-toning agents such as those mentioned above.

Preferably the image-receiving material is prepared by coating onto a support, mostly of paper, a thin imagereceiving layer from an aqueous suspension containing developing nuclei for complexed silver halide and which mostly is coated in such a way that per sq. m. of support from 1 to g. of gelatin or other water-permeable binding agent, from 0.1 to 5 g. of hydroquinone, from 0.5 to 5 g. of anhydrous sodium thiosulfate and from 0.2 to 2 g. of at least one compound selected from the group consisting of alkali metabisulfites, water-soluble inorganic bisulfites and water-soluble aldehyde bisulfites are present.

The light-sensitive material comprises a silver halide emulsion layer and this emulsion layer and/ or a waterpermeable layer which is in effective contact with said emulsion layer usually incorporates such an amount of a 3-pyrazolidone developing compound, that from 0.05 to 0.5 g. of that developing substance are present per sq. m. Occasionally other ingredients such as black-toning agents may also be present in the light-sensitive material.

The emulsion composition is that of a conventionally used emulsion in the art of difiifusion transfer. The emulsion composition is not critical provided its silver salt(s) is (are) capable of development and diffusion in the exposed and non-exposed areas respectively with the rapidity required in diffusion transfer processes. Silver chloride emulsions, which may contain silver bromide or silver iodide, and to which other ingredients have been added so as to impart the desired emulsion characteristics are preferably used. Any such emulsion can be unhardened or slightly hardened.

Preferably the light-sensitive material and/ or the imagereceiving material contains in the uppermost layer (1) at least one water-insoluble metal alginate as described in the French patent specification 1,304,279, or (2) the chromium salt of carboxymethyl cellulose either or not together with at least one water-insoluble metal alginate as described in the French patent specification 1,304,280.

In some circumstances it can be necessary that the concent-ration of alkali in the processing liquid and that the concentration of the products identified above in the lightsensitive material and in the image-receiving material are other than those referred to above.

By adding a 3-pyrazolidone developing substance to the light-sensitive material, whereas the image-receiving material contains hydroquinone, the primary and secondary development stages are caused to proceed so rapidly, that in the most modern developing apparatus for quick treatment very good images are obtained. This is surprising, since the primary and secondary development stages can only proceed when the image-receiving and light-sensitive materials are pressed together by the rollers of the developing apparatus, as the processing liquid most-1y does not contain developing substances and as the developing substances present in the light-sensitive material cause only an initial primary development.

As to the holding off of the complete primary development for so long a time, there can be cited that the secondary developing substance is a poor developer in itself but that the combination of secondary and principal developing substances forms a very active developing composition. A closer explanation of this superadditive effect is given by James, P.S.A. Journal 1953, Section B, p. 156.

According to the present invention there may also be proceeded for instance as follows: a light-sensitive material, containing 1-phenyl-3-pyrazolidone and comprising as top layer a layer for instance of poly(acrylamide) is image-wise exposed and then wetted with treating liquid for instance in the presence of developing substances and of a complexing agent for silver halide. This may occur in different ways for instance by dipping the light-sensitive material in the treating liquid, by moistening it at one side with treating liquid etc. The light-sensitive material thus treated is then pressed against a dry image-receiving material consisting of a baryta-coated paper support to which a layer containing development nuclei and hydroquinone is applied. Immediately thereupon bot-h materials are separated and a diffusion transfer image of excellent quality is obtained on the image-receiving material.

Suitable binding agents for the top layer, from which at least a thin stratum is transferred to the image-receiving material are for instance the following water-permeable colloids: methyl cellulose, the sodium salt of carboxy methyl cellulose, hydroxy ethyl cellulose, hydroxy ethyl starch, hydroxy propyl starch, sodium alginate, gum tragacanth, starch, poly(vinylalcohol), poly(acrylic acid), poly(acryl amide), poly(vinyl pyrrolidone), poly(oxyethylene), copoly( methyl vinyl ether/ maleic acid) etc. The thickness of this top layer varies among others according to the nature of the colloid chosen and the viscosity of the used colloid solution. The water-permeable top layer is preferably not hardened, and may contain the same ingredients which may be present in the other layers of the light-sensitive material.

The diffusion transfer process with a light-sensitive material comprising a top layer from which at least a stratum is transferred to the image-receiving material should also be read in conjunction with the patent application filed on even date herewith for Improved Silver Salt Diffusion Transfer Process. Thus it is also possible to carry out the present invention using an image-receiving material in its top layer in addition to occasional development nuclei and/or substances which may form development nuclei containing a filler. Thus it is also possible to obtain ac cording to the present invention several copies starting from a same image-Wise exposed light-sensitive material and it is also possible to separate light-sensitive and the image-receiving material which are pressed together by applying heat. In the special embodiment of the present invention with an image-receiving material as described in the above mentioned co-pending patent application filed on even date herewith it is thus also possible to obtain almost immediately dry diffusion transfer copies when wetting also the image-receiving material with treating liquid before bringing it into contact with the image-wise exposed light-sensitive material. Finally it has to be mentioned that the present invention should be read in conjunction with the Dutch patent application 288,817, which relates to a device for separating the light-sensitive material from the image-receiving material.

As to the application of this new process, one can proceed according to the existing art of silver complex diffusion transfer using the generally known materials, exposure and developing apparatus as described in Process in P-hotography, volume I, 1940-1950, pages 76, 77 and 140; volume II, 1951-1954, pages 156-7; volume III, 1955-1958, pages 24-36 and in the patent literature cited therein.

The following examples illustrate the present invention.

Example 1 Water cm. 877.2 Gelatin g 40 aqueous sodium sulfide cm. 2.4 10% aqueous cobalt nitrate cm. 13.2 iPotassium metabisulfite g 12.8 Hydroquinone g 6.4 Sodium thiosulfate g 48 This suspension is cast in such a way that 1 liter 12 sq. m. of support are covered.

The light-sensitive material is now image-wise exposed and together with the image-receiving material passed through a diffusion transfer developing apparatus containing a solution of the following composition:

Water cm. 1000 Sodium Phosphate g 100 Anhydrous sodium sulfite g The light-sensitive and image-receiving material are squeezed against each other between the rubber rollers of the developing apparatus and are separated from each other after a contact time of about 10 seconds. A positive print of the Original is obtained.

Example 2 A light-sensitive material is prepared by coating onto a paper support of 90 g./sq. m. a gelatino silver chloride emulsion in such a way that 1.33 g. of silver chloride is present per sq. m. of light-sensitive material. This lightsensitive layer is coated over with a top layer from the following solution in a proportion of 1 litre per 10 sq. m.:

Water cm. 900 PAM 75 (trade name for a polyacrylamide of medium viscosity range marketed by American Cyanamid Company, New York, N.Y., U.S.A.) sg 10 10% solution of 1-phenyl-3-pyrazolidone in ethanol cm. 100 10% aqueous saponine cm. 10

5 This light-sensitive material is image-wise exposed and then moistened with the following treating liquid:

Water cm. 1000 Sodium phosphate g 75 Anhydrous sodium sulfite g 40 Anhydrous sodium thiosulfate g 10 This light-sensitive material is then pressed together with a dry image-receiving material consisting of a paper support of g./sq. m. onto which in a proportion of 1 litre per 40 sq. m. the following composition has been applied at 45 C.:

Water cm. Gelatin g 10 56% aqueous suspension of barium sulfate g 700 Dispersion of cobalt (II) sulfide nuclei as defined hereinafter cm. 35 Hydroquinone g 5 Potassium metabisulfite g 1 1% solution of 1phenyl-5-n1ercaptotetrazole in ethanol cm. 25

The dispersion of cobalt (II) sulfide is prepared at 45 C. from:

Water cm. 78 Gelatin g 2 10% aqueous sodium sulfide cm. 12 10% aqueous cobalt (II) nitrate cm. 11

The materials are then separated from each other. In

this way a practically completely dry positive copy of excellent quality of the original is obtained very rapidly.

The same light-sensitive material can be used now for the production of several positive copies by wetting it again and again with treating liquid, pressing it together with an image-receiving material and then separating it therefrom.

The light-sensitive material wetted with treating liquid can also be pressed together with the dry image-receiving material whilst heat is supplied, for instance by feeding both materials between heated rollers or by first contacting them as usual and thereupon guiding them between heated rollers. The principle of this process is described more in detail in the German utility model 1,794,536. According to these different embodiments with supply of heat, a completely dry positive copy as well as a completely dry negative copy of the original are obtained which even are not to be separated mechanically as they become detached by their own.

Example 3 Example 1 is repeated but by using a light-sensitive material which instead of being coated over with a layer containing PAM 75 (trade-name) is coated over with a top layer from the following solution in a proportion of What I claim is:

1. A process for obtaining photographic images according to the silver complex diffusion transfer process comprising image-wise exposing a light-sensitive material comprising a silver halide emulsion layer and a 3-pyrazoli-- done developing compound, bringing said light-sensitive material in the presence of an alkaline processing liquid into contact with an image-receiving material containing hydroquinone and a member selected from the group consisting of development nuclei and substance capable of forming such nuclei in situ, and separating said materials from each other.

2. A process according to claim 1, wherein the 3-pyrazolidone developing compound corresponds to the following general formula:

wherein:

R is a member selected from the group consisting of an aryl radical and a substituted aryl radical, R is a member selected from the group consisting of a hydrogen atom and an acyl radical,

each of R R R and R is a member selected from the group consisting of a hydrogen atom, an alkyl radical, a substituted alkyl radical, an aryl radical and a substituted aryl radical.

3. A process according to claim 1, wherein the silver halide emulsion layer is a silver chloride emulsion layer.

4. A process according to claim 1, wherein the imagereceiving material comprises at least one compound selected from the group consisting of alkali metabisulfites, water-soluble inorganic bisulfites and water-soluble aldehyde bisulfites.

5. A process according to claim 1, wherein the processing liquid comprises sodium phosphate and sodium sulfite.

6. A process for obtaining photographic images according to the silver halide diffusion transfer process, which comprises image-wise exposing a light-sensitive material comprising a silver halide emulsion layer and bringing this light-sensitive material, in the presence of an alkaline processing liquid, into contact with an image-receiving material containing development nuclei and/or substances capable of forming such nuclei in situ, whereafter these materials are separated from each other, wherein the image-receiving material contains hydroquinone and the light-sensitive material contains a 3-pyrazolidone developing compound, characterized thereby that as a top layer on the light-sensitive material a water-permeable layer is applied from which at least a thin stratum is transferred to the image-receiving material when separating said both materials.

7. A process according to claim 6, wherein only the image-wise exposed light-sensitive material is wetted with treating liquid and this material is then contacted with a dry image-receiving material.

8. A process according to claim 6, wherein the imagewise exposed light-sensitive material after its separation from the image-receiving material is used for the production of further images according to the silver complex difiusion transfer process by contacting it again in the same circumstances with an image-receiving mateiral containing hydroquinone and by separating then said lightsensitive material from said image-receiving material.

9. A process according to claim 6, wherein the contacting step of the light-sensitive material with the image receiving material occurs with supply of heat.

10. A process according to claim 6, wherein the imagereceiving material comprises a support and a top layer containing a binding agent, a filler and hydroquinone.

11. A process according to claim 10, wherein said top layer contains development nuclei and/or substances capable of forming such nuclei.

12. A process according to claim 10, wherein said top layer contains a protein as a binding agent.

13. A process according to claim 10, wherein said up permost layer contains a polymerisation product as a binding agent.

14. A process according to claim 10, wherein the filler is barium sulfate.

15. A process according to claim 10, wherein the filler is china clay.

References Cited UNITED STATES PATENTS 2,751,297 6/1956 Hood et al. 9666 2,834,676 5/1958 Stanley et al 96-29 3,041,170 6/1962 Haist et a1. 96-29 3,067,033 12/1962 Weyde 9628 FOREIGN PATENTS 767,978 2/1957 Great Britain.

NORMAN G. TORCHIN, Primary Examiner. I. TRAVIS BROWN, Examiner. JACK P. BRAMMER, Assistant Examiner. 

1. A PROCESS FOR OBTAINING PHOTOGRAPHIC IMAGES ACCORDING TO THE SILVER COMPLEX DIFFUSION TRANSFER PROCESS COMPRISING IMAGE-WISE EXPOSING A LIGHT SENSITIVE MATERIAL COMPRISING A SILVER HALIDE EMULSTION LAYER AND A 3-PYRAZOLIDONE DEVELOPING COMPOUND, BRINGING SAID LIGHT-SENSITIVE MATERIAL IN THE PRESENCE OF AN ALKALINE PROCESSING LIQUID INTO CONTACT WITH AN IMAGE-RECEIVING MATERIAL CONTAINING HYDROQUINONE AND A MEMBER SELECTED FROM THE GROUP CONSISTING OF DEVELOPMENT NUCLEI AND SUBSTANCE CAPABLE OF FORMING SUCH NUCLEI IN SITU, AND SEPARATING SAID MATERIALS FROM EACH OTHER. 